New Phytologist最新文献

There is much circumstantial evidence that flowering plants were diverse by the Lower Cretaceous and were pollinated by insects (Arber & Parkin, 1907; Crepet & Friis, 1987). Arguments supporting this come from extant and fossil flower morphology, fossilized traces of interactions, and the pollination modes of surviving early lineages. First, some extinct gymnosperms had bisporangiate cones (with both micro- and megasporangia) surrounded by bracts (Fig. 1), and many such cones show traces of having been chewed by mandibulate insects (Peris et al., 2017). Fossils of flower-associated flies also provide evidence of the existence of strobilus–pollinator interactions from the Permian to the Jurassic (Ren, 1998; Ren et al., 2009; Khramov et al., 2023). Second, if flowers evolved from bisporangiate strobili, they were not well suited for wind pollination because simultaneous optimization for pollen export and pollen capture is structurally difficult. The angiosperms' defining enclosure of the megasporangium inside surrounding structures may also point to ancestral insect pollination, as argued by Arber & Parkin (1907: 73), ‘In the case of the angiosperms such primitive entomophily was preserved and rendered permanent by a transference of the pollen-collecting mechanism from the ovule itself to the carpel or megasporophyll and by the closure of this organ.’ Third, all angiosperms, but no living gymnosperm, produce pollenkitt, an oily substance on the surface of pollen that serves as a glue to attach pollen to animal vectors (Hesse, 1980). In wind-pollinated plants, pollenkitt abundance is secondarily reduced. Lastly, the oldest lineages of flowering plants that still survive today are pollinated by flies, moths, and beetles (Luo et al., 2018).

While insect pollination thus undoubtedly played a decisive role in the evolution of flowers, a phylogenetically informed analysis of pollination by insects, vertebrates, wind, and water across a full modern phylogeny of plants has been lacking. This is what Stephens et al. now provide in an article published in this issue of New Phytologist (2023; 880–891). Using a time-calibrated phylogeny with 1201 species representing the major lineages of flowering plants, together with geographic occurrence data, Stephens et al. quantified the timing and environmental associations of pollination shifts. Where possible, they scored pollination at the species level, either from published fieldwork (n = 432) or from the pollinator syndrome approach (n = 728). Where no information was available for a particular species, taxa were scored at genus (n = 131) or family (n = 4) level. In some analyses, 180 taxa with missing or polymorphic data were excluded from the analyses.

All major angiosperm clades (

Carotenoids, once biosynthesised, participate in a range of processes within plants including serving as precursors for the biosynthesis of multiple hormones, acting as signalling molecules and apocarotenoid aroma compounds, as well as playing roles in the stabilisation of photosystems and acting as antioxidants. These functions contribute to a high turnover rate of carotenoids within leaves (Beisel et al., 2010). Another facet of carotenoids is in attracting insects and animals to facilitate successful reproduction and seed dispersal due to their vibrant colours and presence in fruits and flowers. However, this process relies upon their stable storage in the plastids of non-photosynthetic tissue. The quantity and composition of carotenoids is highly species and variety specific, but generally, the total carotenoid content correlates to the colour intensity in these organs. The esterification of xanthophylls (oxygenated carotenoids) to fatty acids positively influences total carotenoid accumulation by enhancing their packaging into specialised structures within plastids, called plastoglobules. Esterification also likely protects xanthophylls from catabolism through steric hindrance of enzymes that catalyse carotenoid cleavage, such as the carotenoid cleavage dioxygenases and the 9-cis-epoxycarotenoid dioxygenases, although this remains to be demonstrated. Despite the positive influence on total carotenoid accumulation, we are only beginning to understand the molecular mechanisms involved in xanthophyll ester production.

Using a comprehensive set of experiments, Li et al. unravel the genetic basis of esterification in rapeseed flowers. Through a combination of map-based cloning, loss-of-function studies using CRISPR/Cas9 technology and genetic complementation, two homologous genes from the esterase/lipase/thioesterase (ELT) family of acyltransferases were identified that function redundantly to direct petal colour formation and are annotated as xanthophyll esterases. The authors used liquid chromatography coupled with UV/vis spectroscopy and high-resolution mass spectroscopy to identify individual xanthophyll ester species, an undertaking which is notoriously difficult (Mercadante et al., 2017). Interestingly, in white petals of both a naturally occurring cultivar and the xanthophyll esterase double knockout line, pcs, not only are esterified xanthophylls absent, but total carotenoid content is greatly reduced, signifying that in addition to biosynthesis, the stable storage and protection of carotenoids from turnover is required to produce the vivid yellow petal phenotype. The authors further probed the metabolome and transcriptome of the xanthophyll esterase double mutant line pcs and discovered that in the white petals of the mutant, metabolic flux is redirected to lipid metabolism and storage. They also observed no change in the expression of carotenoid biosynthesis ge

The development of insecticidal chemicals (commonly termed pesticides) has revolutionized the process of cultivation in agriculture; yet, similarly to the development of antimicrobial resistance in pathogens, insects can rapidly develop resistance to these chemicals (Alyokhin & Chen, 2017). Pesticides can also negatively affect beneficial insects such as pollinators and natural enemies of herbivorous insects (Bourguet & Guillemaud, 2016). Extensive pesticide use also poses risks to farmers and growers who apply the pesticides, as well as consumers who eat the resulting produce (Del Prado-Lu, 2015; Bourguet & Guillemaud, 2016). Additionally, pesticides are not always cheap, increasing the economic burden on farmers and consumers alike (Bourguet & Guillemaud, 2016). As a result, alternative strategies are needed to control major crop pests whose damage affects yield and crop quality. A key component of integrated pest management (IPM) is the identification of extant crop varieties carrying resistance phenotypes against pest insects (Stenberg, 2017), in particular, the identification of varieties or lines that emit deterrent volatile organic compounds (VOCs), which can stop pest insects at the source by preventing physical contact, oviposition, and feeding on vulnerable crops. However, rather than killing the insects once a plant is infested, or in the early stages of infestation, why not just keep the insects from infesting in the first place? An exciting study by Ghosh et al., published in this issue of New Phytologist (2023, 1259–1274) identifies a variety of eggplant (aubergine/brinjal) (Solanum melongena L., Solanaceae) resistant to the eggplant/brinjal shoot and fruit borer (Lucinodes orbonalis Guenée, Lepidoptera: Pyralidae), which infests both the vegetative and fruit tissues of the plant (Fig. 1).

This eggplant variety, which originates in the eastern Himalaya region, shows nearly complete resistance to infestation by the adult moth of L. orbonalis, with a complete lack of infested fruits and shoots, and very limited presence of moth eggs on the leaves of the plant – the moth's usual oviposition site. The identification of a naturally resistant variety of eggplant is exciting news, as the pest moth is found world-wide and can cause the loss of 45–100% of marketable fruit (Reshma et al., 2019). As a result of this heavy infestation and loss potential, eggplant receives some of the heaviest pesticide burdens of any cultivated species, with plants sprayed up to 20 times per month in some locations (Del Prado-Lu, 2015). The presence of these pesticides affects not only the moths, but also potentially beneficial insects such as pollinators and parasitoid wasps. Eggplant is largely self-pollinated but benefits from pollination for seed set and fruit production (Pess